Method and applicator pin for attaching insulator material to ducts by resistance welding

ABSTRACT

A welding pin and method of attaching the same for securing insulator material to ducts. The pin is characterized by an enlarged head portion, a shank extending at right angles to the head portion, terminating in a sharpened tip. The length of the shank is less than the radius of the head portion so that when the pin is supported on a horizontal surface, such as a layer of insulator material disposed above a duct, the included angle between the insulator material and the plane of the head portion is less than 45*.

United States Patent Milton IIinden 15 Bay Link, Massapequa, N.Y. 1175849,253

June 24, 1970 July 6, 1971 [72] Inventor [21] Appl. No. [22] Filed [45]Patented [54] METHOD AND APPLICATOR PIN FOR I ATTACIIING INSULATORMATERIAL TO DUCTS BY RESISTANCE WELDING 5 Claims, 7 Drawing Figs.

[52] US. Cl 219/99, 29/464 [51] Int. Cl 823k 9/20 [50] Field ofSearch219/98, 99;

[56] References Cited UNITED STATES PATENTS 477,587 1892 Albrecht 85/161,241,290 9/1917 Senftner... 85/16 Primary Examiner-J. V. TruheAssistant Examiner Robert E. ONeill Attorneys-Mark T. Basseches andPaula T. Basseches ABSTRACT: A welding pin and method of attaching thesame for securing insulator material to ducts. The pin is characterizedby an enlarged head portion, a shank extending at right angles to thehead portion, terminating in a sharpened tip. The length of the shank isless than the radius of the head portion so that when the pin issupported on a horizontal surface, such as a layer of insulator materialdisposed above a duct, the included angle between the insulator materialand the plane of the head portion is less than 45.

METHOD AND APPLICATOR PIN FOR ATTACI-IING INSULATOR MATERIAL T DUC'IS BYRESISTANCE WELDING The method of attaching the pin includes the steps ofadvancing a planar welding electrode toward the insulation in aperpendicular path, the electrode functioning, with progressivemovement, to tilt the pin and finally, after the tip of the pin isengaged against the duct or substrate, to force the head of the pin intoa parallel relation to the under surface of the welding electrode.

Preferably, the flow of welding current is initiated responsive tosensing of a predetermined selected pressure of the welding electrodeagainst the head of the pin.

The present invention relates to the method of attaching insulatormaterial, such as fiberglass batts or the like, to a duct or large sheetmetal section which is subsequently formed into a duct by bending in abrake, etc.

In heating and air conditioning systems, the current practice involvesthe application of batts or slabs of insulating material to a duct or tometal to be formed into a duct. Insulated ducts are, of course, moreefficient in that heat exchange, due to exposure of the duct to ambientconditions, is minimized.

In my aforementioned copending application, there is described a methodfor securing insulating material to ducts or sheet metal components byresistance welding to assure a secure connection, without damaging theinsulating material. The sheet metal to which the insulation is to beapplied may be elongated and of considerable width, in the area of4 to 6feet or more.

In a copending application filed on even date herewith, and entitledWELDING APPARATUS, there is described a welding device which may beadvantageously employed in affixing a pin to the duct by a welding step.Briefly, the welding apparatus is shiftable linearly along a path aboveand transverse to an elongated piece of sheet metal of substantialwidth.

It is necessary, in devices heretofore used, to position the weldingpins relative to the insulating material either manually by some form ofjig, or by disposing the same in a chuck on the welding apparatus.Application of the pins to the jig or to the chuck is a time-consumingoperation, interfering with mass production techniques. Further, it isevident that the pins, after welding, must be removed from the jig orchuck, involving still further time wastage.

In an alternate manner of application, it is possible in some instances,i.e. in the use of narrow metal strips, for the worker manually to forcethe welding pins into position across the width of the strip byphysically inserting the points through the insulating material.However, this manner of application is impractical where considerablewidths of sheet metal are involved, since it is obvious that a singleworker will not be able to lean across or otherwise reach the remoteside of the metal strip.

The present invention is directed to a welding pin member having aparticular geometric configuration which enables the pin, when used inconjunction with a yieldable insulative material such as a fiberglassbatt, to be automatically tilted and aligned in precise perpendicularrelation to the sheet metal. The pin in accordance with the inventionmay be laid haphazardly atop the insulator so that the weight of the pinis supported in part by the tip and in part by an edge portion of thehead engaging the insulative layer. When the planar welding electrode isbrought down against the uppermost portion of the head, the pin isautomatically tilted and advanced toward the duct, ultimately to assumethe desired perpendicular orientation.

In accordance with an additional embodiment of the method, the weldingcurrent flow is initiated responsive to the sensing of a back pressureagainst the welding electrode developed through the pin. The pressurerequired to initiate a welding cycle is greater than the pressurerequired to bend the head relative to the shank of the pin. Thus, if bysome mischance a pin fails to be aligned and the welding head is currentand there will, thus, be no likelihood that the pin will be misattached.5

SUMMARY OF THE INVENTION A welding pin for attachment by resistancewelding through a batt of readily compressible insulative material to aduct or sheet metal surface disposed beneath the material.

The pin is characterized by a shank portion terminating in a sharpenedtip at one end, the other end of the shank being affixed to or integralwith an enlarged head. The length of the shank from the head to the tipis less than the radius of the head, whereby when the pin is disposedatop an insulative layer, with the tip and edge portion of the headengaging the layer, the included angle between the surface of the layerand the head will be less than 45.

Since the pin is used with a readily compressed insulating layer, itwill be obvious that, due to the diminished surface area of thesharpened tip as contrasted with the area of the edge of the head,pressure applied by a weldingelectrode will cause the pin to pivot aboutthe engaging portion of the head as a fulcrum rather than the tip, dueto the lesser resistance of the tip to penetration and to the angle ofthe head relative to the insulator layer.

The method includes the steps of disposing the pin on the upper surfaceof an insulating layer and advancing an electrode in a perpendicularpath with respect to the sheet metal, the under face of the electrodebeing parallel to the sheet metal. The electrode continues to beadvanced, causing the pivotal movement of the pin aforesaid, inducingthe head to become progressively aligned with the plane of the electrodeand advancing the tip of the pin into contact with the sheet metal.Continued pressure induces a flow of welding current, causing theformation of a weld.

The welding current cannot flow where a pin, by some mischance,maintains an inclined relationship relative to the sheet metal since, insuch circumstances, the head of the pin will bend relative to the shankbefore the pressure required to initiate the welding circuit can bedeveloped.

It is accordingly an object of the invention to provide an improvedwelding pin for the attachment by resistance welding of an insulativelayer of material to sheet metal or to a duct.

A further object of the invention is the provision of a welding pin ofthe type described of a geometry in which the pin will automaticallyalign itself in the desired perpendicular orientation of the shankrelative to the sheet metal responsive to continued movement of thewelding electrode.

A further object of the invention is to provide a method for applyingwelding pins to a sheet metal or like substrate wherein it isunnecessary manually to orient the pin relative to the duct or sheetmetal.

To attain these objects and such further objects as may appear herein orbe hereinafter pointed out, reference is made to the accompanyingdrawings, forming a part hereof, in which:

FIG. 1 is an enlarged view of a welding pin in accordance with theinvention;

FIG. 1a is a view similar to FIG. 1 showing the welding pin of thepresent invention supported on its side on a flat surface;

FIGS. 2 to 5 are sequential views showing the series of steps ofattachment of the pin to a sheet metal substrate through an insulativebody, the welding apparatus being diagrammatically illustrated;

FIG. 6 is a view similar to FIGS. 2 to 5, showing the disposition of theparts where a misformed or misaligned pin is attempted to be welded.

Referring now to FIG. 2, there is diagrammatically shown a weldingapparatus 10 including an electrode 11 having a flat under surface 12.As illustrated thereon, the electrode 11 includes an upwardly directedguide column 13 slidably extending into the housing 14 connected to adrive mechanism (not shown) which is capable of forcing the housing 14in a vertical direction toward the sheet metal substrate 15. A suitablewelding assembly for attaching the welding pin and performing thewelding method of the present application is disclosed in detail in myapplication filed on even date herewith, entitled WELDING APPARATUS. Theelectrode 11 is normally biased downwardly in the housing by a springmember 16, it being understood that the slide connection between theguide column 13 and the husing 14 is effected through the intermediaryof an insulator or insulators so that the electrode is not in conductiverelationship with the housing. Thus, the electrode is provided with alost motion coupling to the housing 14'which is attached to the drivemechanism.

A switch 17 is mounted to the column, the switch including a contactoperator plunger 18 which is upwardly directed toward an under surface19 of the housing 14. It will be appreciated that when sufficientpressure is developed against the under surface 12 of the electrode, thecolumn 13 will move upwardly relative to the housing against thepressure of spring 16, causing the switch 17 to be closed by theengagement of the plunger 18 against the portion 19.

The electrode 11 is connected by lead 20 to the secondary 21 of awelding transformer 22, the other secondary or ground lead 23 beingconnected to the substrate 15, which is likewise grounded. The primary24 of the transformer 22 is connected so as to be activated when thecontacts of switch 17 are closed, either directly or preferably throughthe intermediary of a relay and timing mechanism for controlling theeffective period of flow of welding current.

The showing of the welding apparatus proper is diagrammatic for purposesof simplicity, and no claim to such apparatus is made in thisapplication.

Referring now to FIG. 1, there is shown the welding pin 25 whichprovides a primary advance of the present application. The welding pinincludes an enlarged head portion 26, a shank portion 27 extendingperpendicularly thereto, and a sharpened tip portion 28 at the distalend of the shank. As noted in my coperiding application Ser. No.797,603, it is imperative that the tip of the welding pin be extremelysharp, adequate sharpness being provided by lathe turning procedures. Asnoted in said application Ser. No. 797,603, conventional nail pointingdevices have not been able to produce a point having the requisitesharpness and, thus, resort has been made to the more expensivelathe-turning techniques.

The size relationship of the head 26 of the welding pin relative to theshank 27 of the pin forms an important feature of the present invention.

l have discovered that for purposes of satisfactory operation, it isimportant that the length S of the shank 27 not exceed the radius R ofthe head 26 of the pin. The importance of this relationship is bestappreciated by reference to FIG. la wherein the pin 25 is'disposed atopa horizontal surface 29 representing, by way of example, the uppersurface of a batt or slab ofinsulation material 30.

As will be evident from FIG. la, the pin 25 is shown in essentially theposition which is would occupy if it were haphazardly placed atop thesurface 29 of the insulation material 30. As shown in said figure, thesurface 29 lies tangent to the tip 28 and to a lowermost peripheral edgeportion 31 of the head 26. In this position, the angle A includedbetween the under surface of the head 26 and the upper surface 29 of theinsulator material 30 is less than 45. By providing a structure in whichthe noted angular relationship is achieved, the pin, when subjected to avertical downward pressure applied by a flat under surface, such as thesurface 12 of an electrode, will pivot within the insulating materialabout the peripheral edge portion 31 as a fulcrum, tending to shift theupper surface of the head 26 into alignment with the under surface 12 ofthe electrode.

The sequence of attachment steps wherein the head pivots into thedesired relationship is illustrated best by following the sequence shownin FIGS. 2 through 5.

in FIG. 2, the housing 14 carrying the electrode 11 is shown shiftingvertically downward toward the substrate 15.

In FIG. 3 the welding pin has been partially pivoted within the batt ormass of insulating material. As will be readily un derstood, by reasonof the soft nature of the fiberglass material typically used in ducts ofthis type, pressure of large magnitude need not be applied by theelectrode to the pin since the tip of the pin readily penetrates thesoft material of the insulation. The desired pivotal movement iseffected both by reason of the angle at which the uppermost edge 32 ofthe head 26 engages the under surface 12 of the electrode (such anglealso being less than 45) and by reason of the further fact that, due tothe greater area of the periphery of the head than the point or tip 28of the pin, the head will be more resistant to penetration of theinsulator than will the tip.

With continued downward pressure, the parts reach the position of FIG. 4wherein it will be seen that the tip 28 is engaged against the uppersurface of the substrate 15, preventing any further downward movement ofthe tip.

At this point in the sequence of operation, the shank may or may notbe'aligned in precise perpendicular relation to the substrate. However,by reason of the fact that the insulation prevents lateral shifting ofthe shank, continued downward pressure of the electrode will cause thehead 26 of the pin to become precisely aligned with the under surface 12of the electrode, thereby achieving the precise desired orientation ofthe pin. 1

To this point the pressures applied have not been sufficient to compressthe spring 16 and thereby trigger the flow of welding current.

In FIG. 4 the pin has been shown to be in the precise desired alignment,whereupon further downward movement of the housing 14 may not longer beaccompanied by a downward movement of the electrode 11 due to theaforesaid vertical disposition of the pin. When the pin is thusvertically oriented, continued downward movement of the housing 14 willresult in a compression of spring 16 and resultant triggering of awelding current flow by reason of the activation of the switch As notedin my recited coperiding applications, the flow of welding current willresult in fusing of the tip portion of the pin to the substrate 15, toafford a firm resistance welded connection of the pin. 1 1

It is an important feature of the invention that inadvertentmisattachment of a pin to a duct cannot result from the practice of themethod. The desirability of this feature will be appreciated from thefact that after bending of the material into a duct configuration, theinsulator material, in many instances, forms the inside of the duct. Inthe event that a pin were attached angularly relative to the duct, itwould be evident that a sharp portion of the head of the pin wouldproject into the airstream of the duct, or into a pocket defined withinthe insulation material. In such instance there would be a stronglikelihood that whistles or turbulence would occur within the duct.

Misattachment is avoided by the requirement that back pressure of apredetermined magnitude be sensed before the spring 16 may be compressedto a degree necessary to trigger the flow of welding current. If, due tosome mischance, the included angle A is greater than 45, the pin is soconstructed and related to the force needed to trigger the flow ofwelding current that upon application of a downward pressure, the headof the pin will bend relative to the shank before a back pressuresufficient to trigger the flow of welding current, is developed.

By way of example, if the lowermost portion 31 of the welding pin wereto lie within a hollow or cup in the insulation, the angle A may exceed45. Under such circumstances, (and as depicted in FIG. 6), the desiredturning moment wherein the point 28 is directed approximately downwardlytoward the substrate, may not develop and the pin will be pressedsidewisely through the insulation. As shown in FIG. 6, the result ofthis sequence cannot be a misattachment of the welding pin sincecontinued downward movement will merely result in a bending of the headand shank of the pin relative to each other, which bending occurs at apressure less than the pressure required to trip the switch 17.

As will be appreciated from the foregoing, in order for the worker toattach a series of pins, he need merely manually or otherwise disposethe pins atop the insulation batt in a random arrangement, it beingsatisfactory if the pins are inclined relative to the insulator sheet.The worker thereupon brings the electrode down on top of the pins withthe downward pressure serving initially to orient the pins in a desiredperpendicular configuration relative to the sheet metal, and thereafterto cause the flow ofa welding current.

Through the use of a pressure activated welding circuit in conjunctionwith a welding pin so formed that the requisite back pressure toinitiate a welding circuit cannot be achieved unless the desiredperpendicular relationship has already been effected, there iseliminated any possibility of misattachment ofa pin to the duct.

From the foregoing it is evident that there is disclosed an improvedwelding pin and method of attaching the same whereby substantialeconomies may be achieved by way of reduced labor costs and reducedlosses through misattachment of welding pins.

The configuration of the pins is such as to eliminate the necessity forindividually inserting the pins in the chuck of a welding machine or ina jig calculated to orient the pins with respect to the attachmentsurface.

lclaim: I

1. The method of attaching, by resistance welding, a welding pin havingan enlarged planar head portion and a shank extending perpendicularthereto and terminating in a sharpened tip, the length of said shankbeing less than the radius of said head, to a planar work surface whichis covered by an insulative layer in such manner that the shank of thepin is perpendicular to the surface, which comprises the steps ofsupporting the pin on a compressible insulator layer which parallels thesurface with an edge of the head portion and a side portion of the tipengaging the layer, advancing a welding electrode having a planar undersurface parallel with said work surface toward said work surface in adirection perpendicular thereto, causing said under surface of saidelectrode to contact the uppermost part of said head portion,progressively advancing said electrode toward said surface to induce atilting movement in said shank as a result of compression and imbedmentof said pin in said layer, further advancing said electrode toward saidsurface to cause said tip to contact said surface and to cause said headto conform to the plane of the under surface of said electrode, andthereafter causing a welding current to flow through said electrode headand shank, thereby to weld said pin to said surface.

2. The method of claim 1 and including the additional step ofautomatically causing said welding current to flow responsive to theexertion of a predetermined pressure of said elec trode against saidpin.

3. The method of claim 2 wherein said predetermined pressure required toenergize said welding circuit exceeds the pressure required to bend saidwelding pin and modify the angle between said head and shank whereby awelding current flow can only be initiated if said shank isperpendicular to said surface.

4. The method of attaching by resistance welding a welding pin having anenlarged planar head portion and a shank extending perpendicular theretoand terminating in a sharpened tip, said head and shank being relativelybendable when supported on a substantially flat horizontal surfaceengaging a side portion of said tip and a peripheral portion of saidhead by application of a force of a first given magnitude to theuppermost portion of said head in a direction normal to said surface, toa substrate such as a duct surface with said shank perpendicular to saidduct surface, which comprises the steps of disposing said pin on areadily compressible insulator layer which parallels said duct surfacein such manner that the included angle between said shank and said ductsurface is less than and more than 45, advancing a welding electrodehaving a planar under surface parallel with said work surface towardsaid work surface in a direction perpendicular thereto causing saidunder surface of said electrode to contact the uppermost part of saidhead portion, progressively advancing said electrode toward said surfaceto induce a righting tilting movement in said shank as a result ofcompression and imbedment of said pin in said layer, further advancingsaid electrode toward said surface to cause said tip to contact saidsurface and thereby to cause said head to assume the plane of said undersurface of said electrode, and thereafter inducing a flow of weldingcurrent through said electrode, head and shank responsive to sensing ofa force of said electrode against said pin of a second magnitude greaterthan said first magnitude.

5. The method of claim 4 wherein the length of said shank is less thanthe radius of said head.

1. The method of attaching, by resistance welding, a welding pin havingan enlarged planar head portion and a shank extending perpendicularthereto and terminating in a sharpened tip, the length of said shankbeing less than the radius of said head, to a planar work surface whichis covered by an insulative layer in such manner that the shank of thepin is perpendicular to the surface, which comprises the steps ofsupporting the pin on a compressible insulator layer which parallels thesurface with an edge of the head portion and a side portion of the tipengaging the layer, advancing a welding electrode having a planar undersurface parallel with said work surface toward said work surface in adirection perpendicular thereto, causing said under surface of saidelectrode to contact the uppermost part of said head portion,progressively advancing said electrode toward said surface to induce atilting movement in said shank as a result of compression and imbedmentof said pin in said layer, further advancing said electrode toward saidsurface to cause said Tip to contact said surface and to cause said headto conform to the plane of the under surface of said electrode, andthereafter causing a welding current to flow through said electrode headand shank, thereby to weld said pin to said surface.
 2. The method ofclaim 1 and including the additional step of automatically causing saidwelding current to flow responsive to the exertion of a predeterminedpressure of said electrode against said pin.
 3. The method of claim 2wherein said predetermined pressure required to energize said weldingcircuit exceeds the pressure required to bend said welding pin andmodify the angle between said head and shank whereby a welding currentflow can only be initiated if said shank is perpendicular to saidsurface.
 4. The method of attaching by resistance welding a welding pinhaving an enlarged planar head portion and a shank extendingperpendicular thereto and terminating in a sharpened tip, said head andshank being relatively bendable when supported on a substantially flathorizontal surface engaging a side portion of said tip and a peripheralportion of said head by application of a force of a first givenmagnitude to the uppermost portion of said head in a direction normal tosaid surface, to a substrate such as a duct surface with said shankperpendicular to said duct surface, which comprises the steps ofdisposing said pin on a readily compressible insulator layer whichparallels said duct surface in such manner that the included anglebetween said shank and said duct surface is less than 90* and more than45*, advancing a welding electrode having a planar under surfaceparallel with said work surface toward said work surface in a directionperpendicular thereto causing said under surface of said electrode tocontact the uppermost part of said head portion, progressively advancingsaid electrode toward said surface to induce a righting tilting movementin said shank as a result of compression and imbedment of said pin insaid layer, further advancing said electrode toward said surface tocause said tip to contact said surface and thereby to cause said head toassume the plane of said under surface of said electrode, and thereafterinducing a flow of welding current through said electrode, head andshank responsive to sensing of a force of said electrode against saidpin of a second magnitude greater than said first magnitude.
 5. Themethod of claim 4 wherein the length of said shank is less than theradius of said head.